Light-Weight Solar Panels

dlochner · Nov 17, 2025

Panels are big and often heavy.

Panels that use better quality PV cells will tend to be smaller and lighter than similar wattage panels because the PV cells are more efficient and thus fewer are needed.

There is also a trade off between weight and durability. Lightweight flexible panels will be lighter but are more prone to failure due to flexing and the very small wires inside of the panels breaking.

The article below by Nigel Calder describes many of the issues with solar panels. It is a bit dated now, however, the basics are still the same. Pay particular attention to the construction details and the estimated efficiency.d

For comparison, I have 2 150w Solara Panels. These are high end panels and very efficient, they weigh in at about 22 lbs each and are designed for marine use with a 5 year warranty. They weren't cheap.

Advances in Onboard Solar - Professional BoatBuilder: An IBEX Technical Journal

Advances in onboard marine solar technology improved efficiency and lowered the cost. But they also introduced more complexity.

www.proboat.com

Shop Coastal Climate Control

Coastal Climate Control, marine refrigeration, air conditioning, flexible and walk-on solar panels, systems monitoring, and battery solutions, including lithium batteries

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colemj · Nov 17, 2025

Wattage is primarily a function of physical dimension, as this reflects the individual cell efficiency. Larger panels weigh correspondingly more than smaller ones. 45lbs seems heavy for a 200W panel. That is what our 410 bifacial panels weigh.

Flexible panels are much lighter, but also much poorer performance and lifespan.

Mark

TimFromLI · Nov 18, 2025

I have been using the Renogy flexible solar panels for a few years now and I can't complain. I use a 165 watt attached to the deck below the boom. It is fastend with velcro and has't budged in 6 seasons. I use it to keep my 660AH Trojan t105s topped up on a mooring. I don't leave the batteries on when not on the boat. When cruising I have a second 175watt flexible panel they I fasten to my dodger. Last season we spent two weeks on moorings and the two panels provided enough power for the fridge, lights, laptops phones and a keurig in the morning. We were fortuante to have sunny weather for most of the two weeks. The panels are each about 60X29 if I remember right. The new panels in that same size are rated at 200watts today

garymalmgren · Nov 18, 2025

200W is weighing in the 45lb area. Is there lighter panels than that?
Yes. There are a whole variety of lighter panels.

Also, if I wanted to get a 400-500W panel...they are like 6-7' long!!
Yes. The higher the out put the larger the panel.

I was looking to help charge about 400Amp Hrs of LiFePo and thinking solar around 400-600W would be good?
600 W is a decent input to a battery system. However it will be a larger surface area of panels.

By, "help charge" do you mean to top up the battery?
To "top up" batteries you can use small lighter panels.This will all depend on the load that you are pulling out of the battery system.
If you have a little more going in than is being pulled out the batteries will always be in a reasonable state of charge.
See Tim's post #4.

PS the ad that you have posted states "7% smaller, 10% lighter than other panels "
This is meaningless as no dimensions or weight are given.

dlochner · Nov 18, 2025

GeneraiT001 said:
I'm looking at the Renogy 195W Shadow Flux Anti-shading N-Type Solar Panel (x2) + Blue Tooth + 40A Charger + One Core. On sale now, so hopefully a good deal?

Renogy ShadowFlux Anti-shading N-Type Solar Panel

The Renogy ShadowFlux Solar Panel is a revolutionary off-grid power solution. It is 7% smaller and 10% lighter than traditional rigid solar panels. Featuring N-Type solar cells and 16BB technology.

ca.renogy.com

Renogy equipment will garner rave reviews and raving rants, some swear by them others swear at them. I have no opinion other than the standard, "you get what you pay for."

As for the controllers Victron is a better choice as it offers integration with Victron products. The Victron networking system is evolving to be the standard for electrical systems.

While you can use one controller for 2 panels, a more redundant system uses two controllers, one for each panel. If one panel should fail the other panel is still available.

dlochner · Nov 19, 2025

GeneraiT001 said:
If you use a separate controller for each panel....does that affect the charging rate for the batteries? If I have 2 panels in parallel then I can get about 30 Amps total (I know it will never give you the max) as opposed to 2 separate 15 Amp supplies? I'm guessing that it makes no difference?

No problem with the controllers being paralleled. Each will provide the max amount to the electrical system.

The electrical system and the devices do not care where the power comes from, they see all available power as one source if all the sources, batteries, solar panels, alternator, and charger are wired in parallel. In parallel, the batteries can either a power source or a power consumer depending on the loads and the SOC. For example, if the electrical loads are 10a and the panels are producing 15 amps, then 10a go to the loads and 5 amps goes to the batteries. If the loads increase to 20 amps, then 15 amps come from the panel and 5 amps comes from the batteries. If loads drop to 5 amps, then 5 amps come from the panel and 10 amps go to the batteries. Finally, if the loads are 15 amps and the panel producing 15 amps, nothing goes to the battery, it sits idle.

High Current · Nov 19, 2025

GeneraiT001 said:
If you use a separate controller for each panel....does that affect the charging rate for the batteries? If I have 2 panels in parallel then I can get about 30 Amps total (I know it will never give you the max) as opposed to 2 separate 15 Amp supplies? I'm guessing that it makes no difference?

Correct. If anything the two chargers is better because they can optimize production from each panel separately, e.g. if one is shaded.

dlochner · Nov 19, 2025

GeneraiT001 said:
Just so I'm clear...I am not putting the panels in series or parallel. They are all just treated as separate panels.

Correct the panels are not in series or parallel, the controllers are in parallel when they get to the bus bar.

dlochner · Nov 19, 2025

Let's back up a bit here.

Batteries are placed in parallel for a variety of reasons. Once paralleled the batteries act as a single battery. There is no need to charge them individually or discharge them individually, just treat them as one large battery with one connection to the rest of the DC system.

If all charge sources and all loads, are on a single DC+ bus, then they are all in parallel. Note the DC breaker panel with many circuits counts as one load on the DC+ bus, each individual circuit does not go to the DC+ bus.

There is a good basic electrical systems manual on the Victron site. If I remember correctly it is located in the support area of the site. It covers basics with DC systems and more advanced topics. It is well worth the search through the Victron site.

BarryL · Nov 19, 2025

Hi,

This past season I added 2 100W flexible solar panels. They were cheapie amazon panels. Low cost, low weight, not so great performance.

I installed a Victron MPPS 100 | 30 charger / controller. The victron can take variable inputs and will output 12V. I connected two panels in serial so the output was 24V. The benefits of serial is that less wires are required and the wires can be smaller. This makes installation easier.

I used these panels

Amazon.com

The only complicated part of the install was running the wires THROUGH the cabin top. I hired a pro to do that and the wiring. He did a great job.

The panels put out significantly less power than I expected. My panels are located on top of my dodger so they are shaded by the boom and mainsail.

Since my boat is on a mooring and only used a day or two a week and I turned off the fridge and other loads when I was off the boat I had plenty of power when I arrived at the boat.

Barry

dlochner · Nov 19, 2025

GeneraiT001 said:
So I'm guessing the MPPT controller automatically lowers that 24v to 12v or is your boat wired for 24v?

A "12v Panel" does not put out 12 volts, it puts out up to ~23v depending on the sun angle and light falling on the panels. The Controller takes that voltage and reduces it to whatever the controller is programmed for. For an LFP battery bank, the output should be between 13.8 and 14.1v on a 12v system. Now we're getting into the nitty gritty of how to program all the charging sources.

Because the voltage is high, the current (amps) flowing from the panels to the controller is low. After the controller the voltage is lower and the amps higher. For this reason, the wires leading from the panel to the controller can be smaller. For a 200 watt panel 10 ga is more than adequate. To confirm this, check the ABYC Ampacity charts.

To understand this, understanding the relationship between watts, amps, and volts is necessary. Watts are equal Voltage times Amps. So we just do the math. 100w = 24v * 4.16a, If the voltage is reduced to 12v, the amps double to 8.32. The advantage to high voltage is as @BarryL said, smaller wires can be used which are easier to work with, less expensive, and lighter.

dlochner · Nov 19, 2025

GeneraiT001 said:
Question wrt fusing. I was reading something on the Victron site and it confused me (shocker)

"It is good practice to have a breaker between the panel and the MPPT controller to remove voltage from the input to the MPPT controller for trouble shooting. Provided the cable can carry the full rating of the short circuit current of the solar panel, I see no reason to fuse the line or put a breaker in for overcurrent protection. The circuit cannot deliver more than the short circuit rating of the solar panel and provided the cable can carry that current, nothing needs to be protected. A simple switch is all that is required in my view provided the cable is sized accordingly."

So this is telling me that if the wire/cable I'm using is thick enough to handle a short of 6.86 Amps (the 200W panels Short Circuit Voltage value) then I don't need a fuse, but should have a breaker (15A?) just for trouble shooting?

So the wiring would be direct from the solar panel - through a breaker - to the MPPT and then on to the batteries via a bus bar of some sort?

One thing that is not clear in the Victron manuals is the controller must be powered up before the solar panels provide power. If the sequence is reversed, the controller's LEDs will light up, it can be accessed through BT, but won't produce any power. The CB between the panel and controller provides an easy way to cut power from the panels to trouble shoot and to power up the controller in the correct sequence. A lesson learned after a couple of frustrating days. Without those CBs it is necessary to disconnect the panel from the wiring, wait until dark, or cover the panels with a blanket to block light. Much easier to flip a switch.

There are 2 types of power sources, regulated and unregulated. A regulated power source can only produce X amount of power no matter what, alternators, chargers, and solar panels are all regulated, a 50a alternator can only produce 50a and no more. A battery is an unregulated power source, it can dump all of its power in a very short time at rate much higher than the battery's rating. A LFP battery in a direct short can dump 1,000s of amps in a split second even though it may be rated at 100ah. Again it is the math, 100ah is the same as 600 amp minutes or 6,000 amp seconds. The power is all the same, it is just the discharge time that varies. Another example is a starter, it will draw around 250 amps for a few seconds, but that is only about 1ah.

Gotta run, we'll get to fusing next.